Samsung One UI is a custom Android skin for Samsung smartphones and tablets. It is one of the most popular software skins, primarily due to the Korean tech giant being the second-best-selling smartphone brand in the world. If you own a midrange or flagship Samsung device like the recently released Samsung Galaxy S23 Ultra, you've likely used One UI. But what is it exactly, and how does it differ from stock Android? This article takes a closer look at One UI, how it has evolved, and why it'll be sticking around for a long time.